Defrosting arrangement for refrigeration systems



March 10, 1953 L. L. LEWIS Q 2,530,635

DEFROSTING ARRANGEMENT FOR REFRIGERATION SYSTEMS Filed Jan. 19, 1949 FIG. I

INV EN TOR. 7

Patented Mar. 10, 1953 DEFROSTING ARRANGEMENT FOR REFRIGERATION SYSTEMS Leo Logan Lewis, Syracuse, N. Y., assignor to Car- .rier Corporation, Syracuse, N. Y., a corporation of Delaware Application January 19, 1949, Serial No. 71,695

2 Claims.

This invention relates to refrigeration systems and more particularly to means for defrosting the evaporator of the system when frost has collected on the coils in such quantity as to interfere with the efficiency of the system.

- The chief object of the present invention is to provide a refrigeration system including defrosting means for defrosting the evaporator of the system by passing hot gaseous refrigerant therethrough, the hot gaseous refrigerant being pro- .vided by an external heater.

The object of the present invention is to provide defrosting means for a refrigeration system in which an external boiler heats refrigerant, the heated refrigerant being passed through the evaporator coils in heat exchange relation with frost thereon to melt the same and to liquify the refrigerant, the liquid refrigerant being returned to. the boiler, reheated and again passed through the evaporator until defrosting is complete.

A further object is to provide a simple, economical method of defrosting an evaporator in which hot gaseous refrigerant is provided by a boiler, the hot gaseous refrigerant being passed through the evaporator coil to melt frost collected thereon. Other objects of my invention will be readily perceived from the following description.

This invention relates to defrosting equipment for an evaporator or cooling coil of a direct expansion refrigeration system, such equipment comprising a boiler, a heating element in the boiler, connections between the boiler and the evaporator, means for supplying refrigerant from the system to the boiler, means for preventing passage of liquid refrigerant to the evaporator, and means for preventing passage of gaseous refrigerant from the evaporator to the compressor.

This invention further relates to a method of defrosting an evaporator cooling coil in which the steps consist in discontinuing refrigerant flow from the condenser to the coil, actuating a heat ing element to boil refrigerant, passing the hot gaseous refrigerant through the coil in the heat exchange relation with frost on the exterior surfaces thereof thereby melting the accumulated frost and liquifying at least a portion of the refrigerant, returning the liquid refrigerant to the boiler, and continuing the process until frost has been removed to the desired degree.

The attached drawing illustrates a preferred embodiment of my invention, in which:

Figure 1 is a diagrammatic view of a refrigeration system including the defrosting equipment of the present invention; and

Figure 2 is a diagrammatic view of a modification of the present invention.

Referring to the attached drawing, there is shown a refrigerating system including a compressor 2 connected to condenser 3 by discharge line 4. Condenser 3 is connected to a suitable cooling coil or evaporator 5 by liquid line B. The usual receiver '4' and expansion device 8 such as a thermal expansion valve or capillary tube are disposed in liquid line 6 between condenser 3 and evaporator 5. Evaporator 5 is connected to compressor 2 by suction line 9. The above elements form a closed refrigerating circuit of the welllmown compressor-condenser-expander type.

When the system is in operation, moisture from the air being passed over evaporator 5 condenses thereon and forms frost. Frost on the evaporator coil reduces the efficiency thereof with a consequent reduction in the capacity of the system. To remove frost from the exterior surfaces of the cooling coil, the defrosting equipment of the present invention is provided.

Referring to Figure 1, there is shown a boiler l0 containing a suitable electric or other heating element II. A line 12 connects boiler ill with liquid line 6. A valve I3 is disposed in line l2. When valve i3 is in an open position, liquid refrigerant from line 6 flows into boiler Ill to fill the same. The amount of refrigerant supplied to boiler It may be determined with relation to the size of the evaporator. A line 14 connects boiler ill with the entering end of evaporator 5. A valve 55 is disposed in line It to close the line to passage of refrigerant. A line It connects the leaving end of the evaporator with boiler I0.

A valve I7 is placed in liquid line 6 between the receiver 1 and-expansion device 8. When valve I1 is in a closed position liquid refrigerant from the receiver cannot pass to evaporator 5. A valve i8 is placed in suction line 9 to discontinue flow of refrigerant from evaporator 5 to compressor 2. Valve it does not interfere with flow of liquid refrigerant from evaporator 5 to boiler if! during the defrosting cycle.

When it is desired to defrost cooling coil 5, valve l3 in line I2 is opened permitting boiler NJ to fill with liquid refrigerant. When boiler It is filled to a desired extent valve I3 is again closed. Then valves ll and it are closed to discontinue free flow of liquid refrigerant to evaporator 5 and discontinue free flow of gaseous refrigerant from the evaporator 5 to compressor 2. Valve 15 in line It is opened and the heating element H in boiler I i! is actuated to boil off refrigerant in boiler l0.

The hot gaseous refrigerant boiled off by element H passes through line M to evaporator 5 and passes thru the evaporator in heat exchange relation with frost thereon. The hot gaseous refrigerant melts the frost collected on the exterior surfaces of the evaporator and at the same time is liquified, the liquid refrigerant returning to the boiler through line 16 for reheating. The process is continued until the desired amount of frost has been melted from the cooling coils. Then element H is turned off, valve I5 in line M closed, valves I"! and 18 are opened, and normal operation of the refrigerating system is resumed. If desired, automatic means actuated by an increase in pressure or temperature in the evaporator, safety devices, etc. may be provided to regulate the defrosting cycle.

It will be appreciated the size of the boiler and the heating element are proportioned in accordance with the desired rate of defrosting and to the. total amount of frost to be removed from the cooling coils.

In Figure 2, I have illustrated a modification of the present invention. The refrigeration circuit is similar to the circuit shown in Figure, 1. However, boiler H3 is charged with refrigerant during normal operation. of the cooling cycle. A heat plate 19 is disposed in boiler 10. When it is desired to defrost the coolin coil 5, valves 11 and 1-8 are closed and valve in line [4 is opened. The heating element 1 9 is actuated and the hot gaseous refrigerant passed through coil 5- in heat exchange relation with the frost collected on the exterior surfaces thereof as described above.

It will be appreciated in both the systems described above, hot gas line I 3 may be so arranged as to prevent water from freezing in the drain line and the drip pan on the cooling unit. The valves described are manually operable but it will be understood that such valves may be solenoid valves, for example, to permit the defrost cycle to be controlled automatically.

My-invention provides a simple, inexpensive arrangement to permit cooling coils to be defrosted by using refrigerant taken from the refrigerating system. The defrosting esuipment may be manually or automatically actuated as desired.

The invention minimizes the time required for the defrosting operation.

While I havedescribed' a preferred embodiment of my invention it will be understood my invention is not limited thereto since it may be otherwise embodied Within the scope of the following claims:

I claim:

1;. In a refrigeration system, the combination of a compressor, a condenser, an expansion de-' vice and an evaporator disposed in a closed circuit, a boiler, a heating element in the boiler, a first line connecting the boiler to the liquid line of the system, a normally closed valve in said line, a second line connecting the boiler to the leaving end of the evaporator, a normally open valve in the liquid line adapted to prevent passage of liquid refrigerant from the condenser to the evaporator during the defrosting cycle, said normally open valve being placed in the liquid line between the condenser and the juncture of the first line and the liquid line, and a second normally open valve in the suction line adapted to prevent passage of refrigerant from the evaporator to the compressor during the defrosting cy- 016, said second normally open valve being placed in the suction line between the compressor and the juncture of the second line with the suction line.

2. In the methodof defrosting a direct expansion evaporator of a refrigeration system the steps which consist in withdrawing liquid refrigerant from the closed circuit. of the refrigeration system during normal operation of the refrigeration system, collecting the, withdrawn refrigerant in a boiler, then, during abnormal operation of the system, discontinuing flow of re.- frigerant from the. condenser to the evaporator, actuating a heating element. in the boiler to boil off refrigerant in the oiler, passing the hot gaseous refrigerant through the evaporator in heat exchange relation with frost on the exterior surfaces thereof to. melt, the accumulated frost thereby liquefying at least a portion of the hot gaseous refrigerant, returning the liquid refrigerant to the boiler, and continuing the process until frost has. been removed to a desired degree, then preventing passage of refrigerant from the boiler to the evaporator and from the evaporator to the boiler, and resuming normal operation of the system.

LED; LOGAN LEWIS.

REFERENCES, CITED The following references: are, of record in. the file of this patent:

UNITED STATES PATENTS.

Number Name Date 1,819,510 Hebeler- V Aug. 18, 1931 1,970,344), Ruff: Aug..14-, 19.34 2,001,028 Kitzmiller May 14, 1935 2,430,938 Leeson Nov. 18, 1947 2,430,960 Soling- Nov. 18, 1947 2,452,102 Cocanour Oct. 26, 1948 

